In the environment of telecommunications systems there has been a steady trend toward automating what was originally operator assistance traffic. Much current activity is directed to responding to directory assistance calls by processing voice frequency instructions from the caller without operator intervention. The instructions are used by an automatic speech recognition unit to generate data signals corresponding to recognized voice frequency signals. The data signals are then used to search a database for a directory listing to derive the desired directory number. A system of this type is described in U.S. Pat. No. 4,979,206 issued Dec. 18, 1990.
Further examples of use of voice recognition in automation of telephone operator assistance calls is found in U.S. Pat. Nos. 5,163,083, issued Nov. 10, 1992; 5,185,781, issued Feb. 9, 1993; and 5,181,237, issued Jan. 19, 1993, to Dowden et al.
Another proposed use for speech recognition in a telecommunications network is voice verification. This is the process of verifying the person's claimed identity by analyzing a sample of that person's voice. This form of security is based on the premise that each person can be uniquely identified by his or her voice. The degree of security afforded by a verification technique depends on how well the verification algorithm discriminates the voice of an authorized user from all unauthorized users. While it would be desirable to use voice verification to verify the identity of a telephone caller, such schemes to date have not been implemented in a fully satisfactory manner. One such proposal for implementing voice verification is described in U.S. Pat. No. 5,297,194, issued Mar. 22, 1994, to Hunt et al.
In an embodiment of a system described in the Hunt et al. Patent a caller attempting to obtain access to services via a telephone network is prompted to enter a spoken password having a plurality of digits. Preferably, the caller is prompted to speak the password beginning with the first digit and ending with a last digit. Each spoken digit of the password is then recognized using a speaker-independent voice recognition algorithm. Following entry of the last digit of the password, a determination is made whether the password is valid. If so, the caller's identity is verified using a voice verification algorithm.
Various suggestions have been made to improve the reliability of voice recognition. An exemplary approach is described in U.S. Pat. No. 4,718,096, issued Jan. 5, 1988, to William S. Meisel. That patent describes a speech recognition system that utilizes a plurality of microphones on a body to detect the speech of a speaker. First, second and third microphones may respectively detect sounds emanating from the speaker's mouth, nose and throat and produce signals representing such sounds. A fourth microphone may detect the fricative and plosive sounds emanating from the speaker's mouth and produce signals representing such sounds. The signals are passed on to a recognition system.
U.S. Pat. No. 4,999,613, issued Mar. 12, 1991, to Williamson et al. for a Remote Confinement System, describes a system which relies upon voice recognition in addition to a plurality of different, unsupervised tests. The tests include an RF test performed continuously with an RF transmitter attached to the prisoner and a receiver at the remote location, a schedulable voice test performed to identify a person as the specified prisoner, and a breath alcohol test to determine the prisoner's sobriety.
U.S. Pat. No. 5,023,901, issued Jun. 11, 1991, to Sloan et al., for a Surveillance System, describes a surveillance system which integrates voice identification with a passive monitoring mechanism. Each remote station includes a voice verification unit to receive data and command signals from the central station and to input and receive active and passive monitoring signals from a specific individual. This includes an electro-acoustic transducer connected to a microphone for receiving an active signal comprising preselected spoken words. The remote station also includes a receiver element connected to receive a passive signal such as a continuous signal transmitted from a specific individual indicating the individual's presence at the designated locality. An anklet/bracelet transmitter worn by the confined person can be used to generate an RF signal as described in the preceding patent and, in addition, sensors may be provided at points of entry-exit of the premises to automatically transmit a signal indicating use.